Phase 1: The dynamics and predictability of Mediterranean cyclones leading to high impact weather

Summary

This project focuses on the dynamics of Mediterranean cyclones and the factors that determine their predictability. A special focal point will be the prognostic identification of cyclones leading to High Impact Weather (HIW) in the Mediterranean with storms, heavy precipitation and flash floods especially in the area south of the Alps. Additional criteria to the predicted intensity of the cyclones will be considered, because there are numerous cyclones which are not intense but cause severe weather. We will aim at quantifying the sensitivity of Mediterranean cyclogenesis to large-scale forcing due to an upper-level PV streamer at the dynamical tropopause relative to the impact of moist processes and surface fluxes. The role of embedded convection in the energy and water cycle of cyclones will be investigated in detail by numerical modelling and measurements (funded by other sources) in order to distinguish between cyclones with and without potential for HIW. It is foreseen to concentrate on four typical synoptic scenarios: (i) high amplitude trough approaching the Mediterranean from the west, (ii) remnant circulation in the lower troposphere reactivated by an upper tropospheric trough, (iii) streamer reaching the Mediterranean without cyclogenesis, and (iv) lee-cyclogenesis south of the Alps. With its model studies this project will contribute to future missions of the new German research aircraft HALO, to HyMeX the "Hydrological Cycle of the Mediterranean Experiment", and to THORPEX activities coordinated by the THORPEX European Regional Committee. The HALO-project NEPTUN on the “The western Mediterranean as a sensitive region for cyclone formation causing heavy-rain events” has been accepted as a HALO-DEMO-Mission, being coordinated by the applicants of this proposal.

Phase 2: The initiation, development, and predictability of Mediterranean weather on the synoptic and convective scale leading to extreme events

Summary

The project focuses on the dynamics of Mediterranean cyclones and convection and on the factors that determine their predictability. The main goal is the early identification of cyclones and convective systems leading to high impact weather (storms, heavy precipitation, flash floods) in the west-ern Mediterranean basin. We aim at quantifying the sensitivity of Mediterranean weather to large-scale forcing due to upper-level PV anomalies relative to the regional-scale impact of (convective) moist processes and surface fluxes. The role of embedded convection and warm conveyor belts in the energy and water cycle of cyclones will be investigated by numerical modelling in order to distinguish between cyclones with and without potential for HIW. The impact of grid spacing, the method of convection parameterisation, and convection resolving approaches on the initiation of convection and resulting interaction with larger (synoptic) scales will be investigated for selected cases with and without HIW events. Using the TIGGE data base the sensitivity of Mediterranean cyclones on changing initial conditions and their coupling on the upstream flow will be analysed. With its model studies this project contributes to and benefits from the HYMEX project on the hydrological cycle in the Mediterranean.